soc: qcom: soc_sleep_stats: Update driver to support legacy targets

Update driver to support legacy drivers which do not have
separate offset address to read stats. The legacy targets
provided with start and end address.

Change-Id: I241c1b28d23491001d193737ac1bca90a87e9169
Signed-off-by: Raghavendra Kakarla <rkakarla@codeaurora.org>
Signed-off-by: Tushar Nimkar <tnimkar@codeaurora.org>